1. Field of the Present Disclosure
This disclosure relates generally to marine drives, and more particularly to a marine drive capable of efficiently converting the output of powerful marine engines to forward thrust, to provide rotational speed differentials between plural screws driven by a single engine shaft, and to provide variable thrust vector angle of attack.
2. Description of Related Art including information disclosed under 37 CFR 1.97 and 1.98
Kirin, U.S. Pat. No. 1,595,949, discloses a boat comprising a hull having a cylindrical portion and keel supported centrally upon the under side thereof; side fins arranged upon the opposite and extending downwardly and oppositely and obliquely disposed upon the opposite sides of the keel for eliminating the upper locking and rolling effect of water craft, a drive shaft mounted within the cylindrical member and having propulsion conical-shaped members arranged in like end to end relation upon the opposite ends of the drive shaft exteriorly of the cylindrical portion, and the outer sides of the conical-shape members having helically and spiraled positioned plates radiating from the apex of the conical-shaped members and rearwardly in spaced relation to the periphery thereof to whereby the particular water craft may be propelled and impelled from both ends of the craft in a single operation upon the common drive shaft.
Pierce, U.S. Pat. No. 1,910,561, discloses an outboard motor, in combination, a housing enclosing a vertically disposed power shaft, the housing being rotatable about a vertically disposed line, a horizontally disposed propeller shaft disposed at the lower end of the propeller shaft and operatively connected thereto for driving movement therefrom, the propeller shaft projecting both forwardly and rearwardly from the housing, a propeller secured to the propeller shaft forwardly of the housing, and a propeller secured to the propeller shaft rearwardly of the housing, the last mentioned propeller having a greater pitch than the first mentioned propeller.
Stechauner, U.S. Pat. No. 1,813,552, discloses a propelling mechanism, the combination with an underwater housing, of a power transmission shaft journalled in the housing and extending lengthwise thereof and provided with a bevel gear, a sleeve shaft extending at right angles to the first named shaft and journalled in one end of the housing and provided with a bevel gear meshing with the first named gear and having a shoulder exterior of the housing, a propeller mounted on the second sleeve shaft and abutting the shoulder, a third shaft extending at right angles to the first shaft and journalled in the housing and extending through the sleeve shaft and provided with a bevel gear meshing with the first named bevel gear, and a propeller mounted on the outer end of the third shaft, the propellers being of substantially similar pitch ratio and size but of opposite pitch and mounted adjacent each other, the second and third named bevel gears being disposed on opposite sides of the first named bevel gear and being of the same pitch diameter.
Waterval, U.S. Pat. No. 2,691,356, discloses a multiple propeller drive for ships comprising in combination, a ship's hull having an opening therein, a block member mounted inside the hull, a casing supported by the block member, a shaft journalled in the casing, a pulley mounted on the shaft, a coupling at one end of the latter adapted to connect the shaft to a power unit, a strut secured to the hull, a second casing integral with the lower end of the strut, a second shaft having a propeller at each end thereof, and being mounted in the second casing, a second pulley arranged on the second shaft, and a belt mounted on the first and second pulley and adapted to actuate the second shaft, guides for the first shaft and being attached to the end of the first casing; bearing blocks supporting the first shaft, and screws mounted in the latter for vertical movement, and handwheels threaded upon the screws, whereby to adjust the belt drive.
Arneson, U.S. Pat. No. 4,645,463, discloses a marine outdrive attachable to the transom of a boat having an inboard engine. The marine outdrive includes a tubular support casing securable to and extendable rearwardly of the boat's transom and having a ball socket at its rear end. The ball socket receives a ball at the front end of a tubular, propeller shaft carrier having a conical outer surface. A drive shaft connectable to the inboard engine is journalled in the support casing. A propeller shaft is journalled in the propeller shaft carrier and has a propeller mounted thereon at the rear end of the propeller shaft carrier. A universal joint couples the two shafts together, the center of such joint substantially coinciding with the point about which the ball pivots within the socket. Hydraulic steering cylinders are attached to the propeller shaft carrier to pivot the latter about a steering axis extending through the pivot point of the ball. A hydraulic trim cylinder extends between the transom and the propeller shaft carrier to swing the propeller shaft carrier about a laterally extending trim axis extending through the pivot point of the ball. The upper end of the trim cylinder is pivotally mounted on the transom at a location above and vertically aligned with the pivot point of the ball or at a location above and forwardly of such pivot point. Improved fins are provided on the propeller shaft carrier near the propeller to stabilize the boat. The drive shaft of the inboard motor can be directly connected to the joint or offset from the joint and coupled thereto by a vertically extending transmission.
McCormick, U.S. Pat. No. 4,790,782, discloses a marine stern drive for a boat that includes a propeller assembly having a carrier for a pair of concentric drive shafts to which are mounted a pair of closely adjacent fore and aft coaxial surface piercing propellers mounted on a common axis. The carrier also includes a downwardly extending skeg. The shafts are connected to a source of power and drive the propellers in contra-rotating relationship at essentially equal rotational velocities. The carrier is connected to devices for swinging the carrier laterally for steering, and also vertically. A control is provided for positioning and maintaining the carrier vertically such that both contra-rotating propellers are continuously disposed in surface piercing position during normal operation of the drive. The result is that lateral forces created on the propeller carrier by one rotating surface piercing propeller are counterbalanced by the other propeller when the skeg is parallel to the boat centerline. The leading edges of both propellers are relatively sharp for surface piercing, while the training edges of both propellers are relatively blunt.
Brandt, U.S. Pat. No. 4,840,136, discloses a double-propeller drive unit for boats, in which the under-water housing of the drive unit is designed so that the pressure center for the transverse force on the drive housing caused by water flow is located in front of the steering axis of the drive unit.
Brandt, U.S. Pat. No. 4,619,584, discloses a boat propeller drive with double, counter-rotating propellers that is distinguished by the after propeller having one more blade than the fore propeller as well as a smaller diameter than the fore propeller.
Bankstahl et al., U.S. Pat. No. 4,887,983, discloses a chain drive marine propulsion system that employs dual counterrotating propellers. The propellers are mounted to concentric propeller shafts disposed in the lower end of a depending gearcase. The concentric propeller shafts are each provided with a lower sprocket engaging a chain. A counterrotation mechanism is provided for driving the chains in opposite directions, thereby resulting in counterrotation of the propellers. Various embodiments for driving the chains in opposite directions are disclosed.
Newman et al., U.S. Pat. No. 4,932,907, discloses a marine propulsion system that includes a steerable lower gearcase portion and a drive mechanism including a chain drive for driving dual counterrotating propellers. The dual propellers are rotatably mounted to the lower steerable gearcase portion by means of inner and outer coaxially extending propeller shafts. A sprocket is mounted to each propeller shaft, and first and second chain portions extend between the propeller shaft sprockets and a pair of upper drive sprockets, preferably disposed above the water line during boat operation. Coaxially extending inner and outer drive shafts are interconnected with the engine output shaft, and are adapted for counterrotation in response to rotation thereof. The coaxial drive shafts are interconnected with the upper drive sprockets for driving such sprockets in opposite rotational directions, thereby resulting in movement of the first and second chain portions in opposite directions. The longitudinal axis of the inner and outer drive shafts defines the steering axis about which the lower steerable gearcase portion is pivotable.
Bankstahl et al., U.S. Pat. No. 5,009,621, discloses a dual counterrotating propeller drive mechanism for a marine propulsion system that incorporates a torque splitting device which consists of a differential gear means and a ratio gear means. The torque splitting device assigns a selectable fixed fraction of the engine torque to each propeller regardless of power, thrust, and speed conditions. The rear one of the two propellers adjusts its rotational speed relative to the front propeller in response to changes in the front propeller's wake and in this way maintains optimum propulsive efficiency over a wide range of operating conditions. Furthermore, precise matching of front and rear propeller parameters for a given application is no longer required.
Meisenburg et al., U.S. Pat. No. 5,376,031, discloses a marine drive has two counter-rotating surface operating propellers. The lower horizontal torpedo portion of the housing has an upper zone with outer surface profiles along horizontal cross-sections defining wedges with sharp leading tips forming a sharp leading edge for slicing through the water, the sharp leading tips defining the sharp leading edge defining a first line extending downwardly and rearwardly at a first angle relative to vertical. The torpedo portion has a lower zone with outer surface profiles along horizontal cross-sections defining wedges with sharp leading tips defining a second line extending downwardly and rearwardly at a second angle relative to vertical. The housing includes a skeg extending downwardly from the lower zone of the torpedo portion, the skeg having a leading edge defining a third line extending downwardly and rearwardly at a third angle relative to vertical. The third angle is greater than the first angle and less than the second angle. The first, second and third lines all intersect at the same point which point is on the rotational axis of the concentric counter-rotating propeller shafts.
Meisenburg et al., U.S. Pat. No. 5,376,034, discloses a surfacing marine drive that has a drive housing with a fore exhaust passage forward of the vertical bore housing the driveshaft, right and left exhaust passages extending rearwardly from the fore exhaust passage on opposite right and left sides of the vertical bore, and an aft exhaust passage extending rearwardly from the right and left exhaust passages and aft of the vertical bore and discharging exhaust into dual counter rotating surface operating propellers.
Ogino, U.S. Pat. No. 5,575,698, discloses a transmission for a counter-rotational propeller system of a watercraft outboard drive with an increased flow area for exhaust discharge behind the transmission within the lower unit. The transmission includes a pair of counter-rotating gears. A front clutch selectively drives an inner propulsion shaft by engaging the front gear. A rear clutch selectively drive an outer propulsion shaft by engaging either of the gears. The front clutch lies forward of the front gear and the rear clutch is interposed between the gears. The clutching mechanism thus entirely lies forward of the rear gear to provide more space for exhaust discharge flow behind the transmission.
Sambino et al., U.S. Pat. No. 5,759,073, discloses a propulsion system for a marine drive, which includes a pair of counter-rotating propellers, provides improved acceleration from idle or low speeds. Engine exhaust from an engine which powers the marine drive is conveyed to the water about each of the propellers. The exhaust gases aerate the water about each propeller to reduce drag resistance on each propeller. Several embodiments of the propulsion system are disclosed which convey the exhaust gases to both propellers for this purpose.
Alexander, Jr. et al., U.S. Pat. No. 5,766,047, discloses a twin propeller marine propulsion unit for a watercraft. A vertical drive shaft operably connected to the engine is journalled for rotation in a lower gear case and carries a beveled pinion that drives a pair of coaxial bevel gears. An inner propeller shaft and an outer propeller shaft are mounted concentrically in the lower torpedo-shaped section of the gear case and each propeller shaft carries a propeller. To provide forward movement for the watercraft, a sliding clutch, is moved in one direction to operably connect a first of the bevel gears with the inner propeller shaft to thereby drive the rear propeller. When the engine speed reaches a pre-selected elevated value, a hydraulically operated multi-disc clutch is actuated to operably connect the second of the bevel gears to the outer propeller shaft, to thereby drive the second propeller in the opposite direction. With this construction only a single propeller is driven at low engine speeds and the second propeller is driven when the engine speed reaches the pre-selected value.
Iriono et al., U.S. Pat. No. 5,800,223, discloses a marine propulsion device that improves the handling characteristics and the responsiveness of the watercraft on which it is used. The propulsion device includes a pair of counter-rotating propellers. At least the blades of the front propeller each have a mean camber line in cross-section which has a generally constant radius of curvature. This blade shape reduces cavitations and permits the rear propeller to be mounted closer to the front propeller, and consequently closer to the steering axis of the outboard drive. As a result, steering torque is reduced. The blades of the rear propeller also are not more than thirty percent smaller than the blades of the front propeller, and the average pitches of the propellers do not differ by more than one to four percent. These blade configurations of the front and rear propellers improve the stability of the watercraft when turning, thereby reducing chine walk, as well as improve the responsiveness of the watercraft.
Sumino, U.S. Pat. No. 5,807,151, discloses a blade design for a counter-rotating propeller system that improves the performance of the outboard drive on which is it employed when the propellers are run partially exposed. The propeller system includes a pair of counter-rotating propellers that rotate in opposite directions about a common axis. The rear propeller has a smaller diameter—about 92% of the front propeller—and a total blade face surface area of about 85% of the total blade face surface area of the front propeller. The blades of the front and rear propellers desirably have the same camber and generally the same pitch. The rear propeller pitch is between 90% and 110% of the front propeller pitch. These blade parameters improve the efficiency of the rear propeller over prior designs when the propellers run partially exposed in order to maximize the thrust produced by the propulsion system.
Jordan, U.S. Pat. No. 6,821,169, discloses a hybrid gear/sprocket-based transmission for driving a pair of coaxial, counter-rotating propellers in vessels. A drive shaft couplable to an engine crank shaft extends rearward into the transmission case, and a pair of coaxial driven shafts extend rearward out of the transmission case, to which are attachable a pair of propellers. A gear train, containing an even number of gears, reverses the rotational direction of the engine; a flexible member retains the rotational direction of the engine. Improved stability characteristics are imparted by supporting the drive shaft at two points and also by positioning the drive and the driven shafts in vertical alignment.
Reuter et al., U.S. Pat. No. 6,899,576, discloses a watercraft drive for a watercraft having front and rear propellers respectively mounted on a drive shaft in coaxial longitudinally displaced relationship, each of said propellers having at least two blades, the front and rear propellers having equal diameters and being driven at like rotational velocities. The central portion of the rear propeller up to a diameter equal to the diameter of the water jet arriving at the rear propeller, which due to the action of the front propeller has a contracted cross section, is designed to optimize the jet energy exiting the front propeller. The rear propeller has an annular area extending from the central portion to the outer circumference of the rear propeller, being designed with the same design as characterizes the front propeller. The annular area of the rear propeller receives a flow of surrounding ambient water.
The related art described above discloses outboard drives, L-drive arrangements and also near coaxial drive shaft-screw axis drives. Only the later is significant relative to the present disclosure. The former marine drive types generally provide a right angle drive train which is not of interest because of its relatively lower efficiency. However, Sage, U.S. Pat. No. 6,431,927, Arneson, U.S. Pat. No. 4,645,463, McCormick, U.S. Pat. No. 4,790,782 and Jordan, U.S. Pat. No. 6,821,169 all coaxial drives which are applicable to larger water craft such as yachts. All but McCormick also teach the use of a mechanism for adjusting the angle of attack of marine screws.
The present disclosure distinguishes over the prior art providing heretofore unknown advantages as described in the following summary.